Aside from scissors, glue, ruler and tape, which are all likely in supply at your place anyway (because you'll need those pretty much all the time), you'll find that the below listed supplies will carry you a long way on the toddler arts and crafts front. All of these items are pretty inexpensive, so it'll be cheap and easy to build up your stash!
* Googly eyes. Just trust me. They come in small bags of assorted sized eyes. Get that one. The kind that are self adhesive are sometimes convenient so that you don't have to glue them on.
* Coffee filters. Don't believe me? Look at the cool ideas here and here. And that's just for starters. Oodles of oohs and ahhs for a couple of bucks.
Your arsenal should be pretty well stocked if these items are included in your craft stash. You'll be able to tackle just about any basic craft project that comes your way! Now you can roll up your sleeves and feel prepared as you look to get crafty with your kids. Have a wonderful weekend, everyone!